Australia’s most complete sauropod skull reveals link with dinosaurs in South America via Antarctica

A 95-million-year-old skull found at the Winton formation in Queensland is the most complete sauropod skull fossil in Australia.

The skull belonged to a Diamantinasaurus matildae and is the fourth specimen of the species found in the Winton area, 1350km north west of Brisbane.

The third, Ollie, was announced last year and was just a baby, being Australia’s smallest sauropod ever discovered.

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Diamantinasaurus are a type of titanosaur – a part of the sauropod family of dinosaurs known for their long necks and tails, and massive size. Some titanosaurs grew to 40 metres in length and are estimated to have reached at least 100 tonnes making them the largest land animals ever.

Nicknamed Ann, the newly-described dinosaur’s fossils were first excavated in 2018.

Ann would have been a subadult, 15 metres long and weighing 20–22 tonnes – as much as four African elephants. Fully-grown Diamantinasaurus may have been more than 20 metres long.

Dr Stephen Poropat – a Museum Research Associate and Postdoctoral Research Fellow at Curtin University in Perth, WA – says that finding the skull of an extinct animal is crucial in understanding its behaviour, what it eats, and how big its brain is.

“Diamantinasaurus has a rounded snout,” Poropat tells Cosmos. “Among sauropods, that is seemingly a very good indication that it’s not browsing low down to the ground.”

Poropat explains that this confirms previous Diamantinasaurus tooth finds which show no signs of wear from grit which would have been an indication of low-lying vegetation consumption.

“So this animal is almost certainly feeding at least one metre above the ground, and probably up to six or seven metres above the ground,” Poropat says. Exactly what kind of vegetation it was eating remains a bit of a mystery though.

Winton today is flat sheep grazing country. 95 million years ago, Poropat explains, it would have been lush, wet floodplain home to conifers, cycads, ferns and plant species now extinct in Australia such as gingko and horsetail.

Though not as many specimens have been found as Diamantinasaurus, other fauna inhabiting the region alongside Ann were meat-eating therapod dinosaurs, crocodiles and flying reptiles.

Ann’s skull also adds weight to earlier suggestions that Australian titanosaurs are closely related to South American sauropods.

Sarmientosaurus musacchioi, which lived in what is now Argentina at around the same time as Diamantinasaurus lived in Queensland, is known from a very well-preserved skull, but little else. Ann’s skull now allows palaeontologists to see their close similarities.

“It’s shoring up our idea that titanosaurs seem to have taken advantage of a period of extreme global warmth between 100-95 million years ago. At that time, Australia is still connected to Antarctica via Tasmania and South America has a sort of island connection with Antarctica,” Poropat explains.

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Sauropods tend to prefer warmer climes, but in hotter periods of Earth’s history, it seems they were able to move further south. This is supported by the discovery of close relationships between Australian and South American titanosaurs.

Poropat says that we have barely scratched the surface of what can be found in Winton and around Australia.

It points to the importance, Poropat comments, of citizen science and involving ordinary people in the discovery, digging and preparation of fossils through the Australian Age of Dinosaurs Museum’s engagement programs.

“It’s great. You get people in the public who are really engaged when our papers come out. They say; I dug that fossil up, I prepared that fossil. It has some sort of personal relevance to them,” Poropat says.

The research is published in the journal Royal Society Open Science.